Rasheed Wallace is already behind the 8-ball, and coach Mike Woodson sounded frustrated. Wallace missed the Knicks’ first practice — a three-hour workout heavy on conditioning — because his contract is not finalized.

Agent Bill Strickland told The Post he’s still hammering out the final “minor details” of Wallace’s pact, and “I fully expect and anticipate Rasheed will be with the Knicks this season and it should be very soon.’’

When the media was let into the gym 2 ½ hours into practice, Wallace, 38, wasn’t on the court. Sources said he was in the locker room, presumably working out. It’s unclear if he participated in some of the conditioning drills earlier.

“We’re trying to get a contract together, so right now he’s not part of the team,’’ Woodson said.

Wallace, 38 and coming out of retirement after a two-year hiatus, will sign for the $1.7 million veteran’s minimum, which likely won’t be fully guaranteed unless he makes the club.

“He’s not here for the money, he’s here to win a ring,’’ Strickland said.

***

Tyson Chandler celebrated his 30th birthday Tuesday, as players sang to him after their first practice. That makes six players 30 and over on the Knicks roster.

Now a statistical study is branding the Knicks the oldest team in NBA history, with an average age of 32.7. STATS LLC made the assessment based on the team’s top 13 players.

Chandler thinks the age talk is a good thing, saying the Knicks were too young last season. The Post reported Sunday the Knicks are the first team since 2000-01 to field five players over 35.

“The guys we do have are going to bring great veteran leadership and bring a calmness about the team we didn’t have before,’’ Chandler said.

“It’s going to benefit us. In order to win in this league you’ve got to have veterans. All those guys bring different elements to the team we didn’t have last year. We had a lot of young guys but we were all over the place. We won basketball games. It was exciting, [we] had our ups and down. It wasn’t consistency. Veterans like this brings consistency.’’

***

Chandler and Jason Kidd, 39, both parroted general manager Glen Grunwald, saying their 2011 Dallas title team had an average age of 30.4.

“A lot of people talk about age,’’ Kidd said. “But athletes are playing a little longer now, which is great.’’

Another age milestone occurs Thursday. Kurt Thomas, the oldest player in the NBA, turns 40.

***

The Knicks have added two assistants, — Jerry Dunn, former Penn State head coach, and former NBA veteran LaSalle Thompson, a teammate of Woodson’s with the Kings.

Dunn was 117-121 in eight years at Penn State, resigning in 2003. His last job was associate head coach at Michigan, leaving in 2009. Woodson also has Chris Ford as coaching consultant and Dave Hopla as shooting coach.

***

Woodson said he ditched two-a-days in training camp after his third Atlanta season, and instead is conducting one three-hour practice daily.

“I found out the body gets enough time to recover,’’ Woodson said. “They get a good night’s sleep and are ready to go the next day. I’m done with two-a-days. I just don’t believe in them.’’